004 What is the cloud made of?

Initially, the bottle contains alcohol vapour, which is invisible to our eyes.

00Picture1When the pressurized air in the bottle is suddenly allowed to expand, it undergoes what is called an adiabatic process. During an adiabatic expansion, a gas does work to expand against the external pressure with negligible heat transfer from its surrounding. When a gas expenses its internal energy this way, its temperature drops. The chill in the bottle causes the alcohol vapor to condense into visible alcohol clouds.


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